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GETITIMER(3P)              POSIX Programmer's Manual             GETITIMER(3P)
PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
NAME
       getitimer, setitimer -- get and set value of interval timer
SYNOPSIS
       #include <sys/time.h>
       int getitimer(int which, struct itimerval *value);
       int setitimer(int which, const struct itimerval *restrict value,
           struct itimerval *restrict ovalue);
DESCRIPTION
       The getitimer() function shall store the current  value  of  the  timer
       specified  by  which  into  the  structure  pointed  to  by value.  The
       setitimer() function shall set the timer  specified  by  which  to  the
       value  specified in the structure pointed to by value, and if ovalue is
       not a null pointer, store the previous value of the timer in the struc-
       ture pointed to by ovalue.
       A  timer  value  is  defined  by  the itimerval structure, specified in
       <sys/time.h>.  If it_value is non-zero, it shall indicate the  time  to
       the  next timer expiration.  If it_interval is non-zero, it shall spec-
       ify a value to be used in reloading it_value when  the  timer  expires.
       Setting it_value to 0 shall disable a timer, regardless of the value of
       it_interval.  Setting it_interval to 0 shall disable a timer after  its
       next expiration (assuming it_value is non-zero).
       Implementations  may place limitations on the granularity of timer val-
       ues. For each interval timer, if the requested timer value  requires  a
       finer  granularity  than  the implementation supports, the actual timer
       value shall be rounded up to the next supported value.
       An XSI-conforming implementation provides each process  with  at  least
       three interval timers, which are indicated by the which argument:
       ITIMER_PROF   Decrements both in process virtual time and when the sys-
                     tem is running on behalf of the process. It  is  designed
                     to be used by interpreters in statistically profiling the
                     execution  of  interpreted  programs.   Each   time   the
                     ITIMER_PROF  timer  expires, the SIGPROF signal is deliv-
                     ered.
       ITIMER_REAL   Decrements in real time. A SIGALRM  signal  is  delivered
                     when this timer expires.
       ITIMER_VIRTUAL
                     Decrements in process virtual time. It runs only when the
                     process is executing. A  SIGVTALRM  signal  is  delivered
                     when it expires.
       The  interaction between setitimer() and alarm() or sleep() is unspeci-
       fied.
RETURN VALUE
       Upon successful completion, getitimer() or setitimer() shall return  0;
       otherwise, -1 shall be returned and errno set to indicate the error.
ERRORS
       The setitimer() function shall fail if:
       EINVAL The value argument is not in canonical form. (In canonical form,
              the number of microseconds is a non-negative integer  less  than
              1000000 and the number of seconds is a non-negative integer.)
       The getitimer() and setitimer() functions may fail if:
       EINVAL The which argument is not recognized.
       The following sections are informative.
EXAMPLES
       None.
APPLICATION USAGE
       Applications  should  use the timer_gettime() and timer_settime() func-
       tions instead of the obsolescent getitimer() and setitimer() functions,
       respectively.
RATIONALE
       None.
FUTURE DIRECTIONS
       The  getitimer()  and  setitimer() functions may be removed in a future
       version.
SEE ALSO
       alarm(), exec, sleep(), timer_getoverrun()
       The Base Definitions volume of POSIX.1-2008, <signal.h>, <sys_time.h>
COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal and Electronics Engineers,  Inc  and  The  Open  Group.   (This  is
       POSIX.1-2008  with  the  2013  Technical Corrigendum 1 applied.) In the
       event of any discrepancy between this version and the original IEEE and
       The  Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be  obtained  online
       at http://www.unix.org/online.html .
       Any  typographical  or  formatting  errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files  to  man page format. To report such errors, see https://www.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                        GETITIMER(3P)